On-Site Wastewater Treatment and Disposal Systems - Forced ...

of about 0.004 lb/cap/day (1.9 mg/cap/day) or 17 mg/l as N in the re-
maining graywater (Tables 4-4 and 4-5). Chapter 5 describes the process
features, the performance, and the operation and maintenance of low-
water carriage and waterless toilet systems. The resultant residuals
from toilet segregation, whether they be ash, compost, chemical sludge,
or blackwater, must be considered in this treatment strategy. A dis-
cussion of residuals disposal is presented in Chapter 9.
The success of this method of nitrogen removal is dependent upon appro-
priate management of the in-house segregation fixtures and the disposal
of the residues from them. These devices must be considered a part of
the treatment system when developing appropriate authority for institu-
tional control.
6.6.2.3 Biological Processes
Nitrogen undergoes a variety of biochemical transformations depending
upon its form and the environmental conditions (61). Organic nitrogen
in domestic wastewaters readily undergoes decomposition to ammonia in
either aerobic or anaerobic conditions. In an aerobic environment, a
select group of bacteria oxidize ammonia to nitrite and ultimately
nitrate. Nitrates may be reduced by a variety of organisms to various
nitrogen gas under anaerobic conditions. Depending upon the treatment
objectives, one or several of these processes may be employed to achieve
the desired end product.
a. Applicability
A number of biological processes for nitrogen conversion are applicable
to onsite treatment. Domestic wastewater characteristics should not
limit application of these processes, provided the nitrogen is in the
appropriate for-m for conversion. Since biological processes are tem-
perature-sensitive, such systems should be covered and insulated in cold
climates. Covering also contains odors, should problems occur.
b. Process Performance
Although data are sketchy, about 2 to 10% of the total nitrogen from the
home may be removed in the septic tank with septage (63)(64). Approxi-
mately 65 to 75% of the total nitrogen in septic tank effluents is in
the ammonia-nitrogen form, indicating a significant level of decomposi-
tion of organic nitrogen (2).
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